Corps: Be wary of delta’s bendway weirs
CLARK FORK — The U.S. Army Corps of Engineers is warning boaters to be on the lookout for bendway weirs in the Clark Fork Delta.
Bendway weirs are low-level rock dikes angled upstream to the flow and are typically submerged at all times.
The structures cause a widening of the navigation channel, mainly in bends or turns, by creating a favorable redistribution of velocities and sediments.
Twelve of the weirs were installed this spring on the north side of Derr Island to Johnson Point for bank stabilization as part of the Clark Fork Delta island-building project. The rock jetties extend from the shoreline perpendicularly 100-200 feet into the river channel.
“These extend a short way into the main channel that runs along these islands in order to slow and redirect the flow away from the banks,” said Evan DeHamer, a staff biologist and mitigation specialist with the Idaho Department of Fish & Game.
They are expected to be submerged and not readily visible to boaters when the lake level reaches 2,053-2,054 feet above sea level.
DeHamer said several emergent benches were constructed on the lee side of the breakwaters, and planted where appropriate with willows and dogwood. Plans are pending this spring/summer to plant these benches and breakwater area with native sedges, rushes, forbs and shrubs.
“We will also be placing a modest amount of additional rock on 2015’s Phase 1 island breakwaters between White/Derr and the Driftyard to improve their performance,” DeHamer said.
Improvements were also made to the Johnson Creek access area and boat launch to improve recreation and guard against erosion, DeHamer added.
“The intent of the overall project is to reduce or stop the loss of the remaining important, productive freshwater delta habitat, the majority of which has been lost or impacted by Albeni Falls and Cabinet Gorge dam operations,” DeHamer added.
Keith Kinnaird can be reached by email at kkinnaird@bonnercountydailybee.com and follow him on Twitter @KeithDailyBee.
